Legal Question in Real Estate Law in California

Yes, the City has the power to condemn it as a health and fire hazzard. They might even try to get their consent to a psychiatric examination. Afterall, such behavior is abberant and needs to be treated. How far the local government will go depends upon the personality of the person in charge and what the surrounding buildings look like. You need to find someone they trust who can get them to agree there is clutter and some of its needs to be thrown away, and then announce the date and time people will come over to reduce the mess. Get as many people as you can to help so that when after 30 minutes they object to the further removal a lot has been done, adn schedule specific return clean up dates.

Try to get them to see counseling. They probably are also cheap in spending so you may have to buy a cpuple of visits for them. Try to appeal to what they care about: if the paper is recycled how many treees would be saved. But also warn them that if their house remains that way and the insurance company for the house learns of its condition it will cancel coverage. The house is much more of a fire hazzard.

I have a friend with the same problem, so I know it will not be easy.

Yes, it can be condemned. Your proper remedy is to get it completely cleaned up immediately and bring it into compliance with building and safety codes, then seek re-inspection and removal of the condemnation order. You'll need the help of an attorney with the legal side, possibly including obtaining conservatorship or guardianship over the grandparents. Feel free to contact me if serious about doing so.